The present invention relates to methods and apparatus for weighing a sucker-rod pumped well, and more particularly, to methods and apparatus for checking various portions of the apparatus by weighing the well.
Sucker-rod type pumping units are widely used in the petroleum industry in order to recover fluid from wells extending into subterranean formations. Such units include a sucker-rod string which extends into the well and means at the surface for an up and down movement of the rod string in order to operate a downhole pump. Typical of such units are the so-called "beam-type" pumping units having the sucker-rod string suspended at the surface of the well from a structure consisting of a Samson post and a walking beam pivotally mounted on the Samson post. The upper end portion of the sucker-rod string normally is connected at one end of the walking beam and the other end of the walking beam is connected to a prime mover such as a motor through a suitable crank and pitman connection. In this arrangement the walking beam and the sucker-rod string are driven in a reciprocal mode by the prime mover.
The lower end of the sucker-rod string is connected to a plunger which is moved up and down inside a working barrel of the downhole pump to lift fluid from the pump to the earth's surface. The pump includes a traveling valve mounted on a plunger with the traveling valve designed to lift off a valve seat when the plunger is moving downward through liquid inside the barrel and the traveling valve is closed to lift the fluid as the plunger moves upward inside the barrel. A standing valve at the lower end of the working barrel opens to admit fluid into the barrel as the plunger moves upward, and the standing valve closes to retain fluid in the barrel as the plunger moves downward in the barrel. A length of tubing extending from the pump barrel to the earth's surface carries fluid upward from the pump to a flow line at the surface.
If the tubing should leak or if the traveling valve or the standing valve should malfunction the fluid flow to the surface will be reduced or stopped and damage to other portions of the equipment could result.